For a wireless communication device, such as a broadband wireless communication device, calibration can be performed to assure that accurate radio frequency (RF) power is transmitted at an antenna and antenna connector of the wireless communication device. The calibration can be sensitive to the effects of impedance of the antenna connector. Such impedance can be referred to, or attributable to, voltage standing wave ratio (VSWR) effects.
As bandwidth frequencies increase for wireless communication devices, problems can arise as to providing accurate power and dealing with power amplifier non-linearity. In certain wireless communication device, power amplifier pre-distortion or PAPD algorithms can be performed to calibrate power amplifier (PA) non-linear response. This can be performed by extracting the AM and PM response of the PA. This response can be achieved from a loop-back that exists in the system after the PA output as measured by a detector. Sampled data after the PA may be multiplied by a detector frequency response, which occurs due to VSWR effects at an antenna port or connector. In certain cases the problem can be solved by using an equalizer to extract the original data; however, averaged data (i.e., sampled data) is of interest, and not on the original data itself.
In the case of PAPD for mask correction and limited VSWR, the PA can exhibit some “virtual” filter response before the PA that is translated into memory effects which current PAPD algorithms may not able to deal with. The memory effects are non linear in nature, and can be attributed to impedance change due to the antenna and interfaces (e.g., coupler/connector). From the non linearity and frequency change due to impedance, you get the memory effects. With greater or wider bandwidths, memory effects can become more pronounce in the PA. Therefore, it becomes more difficult to separate out the memory effects from an actual signal, as memory effects increase. Non linear scrambling and linear behavior of a channel formed by the PA are not easily separated.